The purpose of this prospective epidemiological study is to determine whether childhood aggression and social withdrawal are risk factors for mental illness in adulthood. In addition, we are examining whether other negative outcomes, such as social and occupational maladjustment are associated with these patterns of deviant behaviors. Four risk populations are being studied: individuals who as children were aggressive, withdrawn, or both aggressive and withdrawn, and a control sample of individuals who as children were not deviant on either characteristic. These individuals were initially identified in middle childhood when they ranged in age from 6 to 13 years. During this phase of the project, they will be in early adulthood, ranging in age from 21 to 28 years. We have adopted a multilevel data collection strategy. Data will be collected by means of (1) archival records, (2) visits by lay interviewers to individuals' homes to identify psychopathology and to collect additional information predictive of psychiatric distress, such as life stress and social support, and (3) visits by participants to the laboratory for psychiatric interviews conducted by experienced clinicians to obtain detailed psychiatric diagnostic data, and for laboratory tests to obtain information about attention deficits that are frequently associated with major psychopathology. The study is unusual in the large size of the prospective cohort (1,774). It will be possible to detect elevations in risk factors for psychiatric disorders with relatively high prevalence, such as substance use, and for psychiatric disorders with relatively low prevalence, such as, schizophrenia-spectrum disorders. The study is also unusual in having a large representation of females in the risk groups. In the past, particularly in the study of aggression or conduct disorders, it has been common for studies to be base predominantly on male samples. The timing of this phase of the study is propitious. We have the opportunity to assess individuals at the beginning of adulthood. Combined with data from subsequent planned phases of the project that will follow individuals through the period of highest risk for major psychopathology, we will be able to trace the development of individuals from childhood risk factors, to early experiences as adults predictive of psychopathology (e.g. life stress) to the identification of the age of onset of adult mental disorders.